1. Field of the Invention
The present invention relates, in general, to rectangular vacuum gate valves, and, more particularly, to a rectangular vacuum gate valve having an improved driving action, in which a first guide slot precisely guides the upward and downward movement of the valve, and a cane head shaped  second guide slot, the upper end of which is curved, precisely guides forward and backward movement of the valve, thus reliably realizing an L-shaped two-stepped driving action of a main shaft.
2. Description of the Related Art
A slit valve was proposed in Korean Patent Application No. 10-2003-0071906 (title: SLIT VALVE), which was filed by the applicant of the present invention, the slit valve being constructed such that the structure of a sealing member, disposed around a wafer moving passage, is improved so that the sealing member, which openably closes the wafer moving passage, is prevented from being damaged, and the state of the valve, when operated, can be observed using an indicator provided in a valve drive unit.
FIG. 1 is a sectional view showing the conventional slit valve. Referring to FIG. 1, the slit valve of No. 10-2003-0071906 includes a sealing member 100, which opens or closes a wafer moving passage, a housing bracket 200, which is provided separately from the sealing member 100, a main shaft 400, which extends a predetermined length between the sealing member 100 and the housing bracket 200, and a valve drive unit 300, which is provided in the housing bracket 200. The valve drive unit 300 includes air cylinders 310, which are operated by air pressure, pistons 320, which are provided in the respective air cylinders 310, piston shafts 330, which are coupled to the respective pistons 320, a moving unit 340, which is coupled to the piston shafts 330, and a link 350, which is connected between the moving unit 340 and the main shaft 400.
In the conventional slit valve having the above-mentioned construction, the pistons 320 of the air cylinders 310, which are provided in the housing bracket 200, are moved upwards or downwards, depending on a change in the pressure of compressed air supplied into the air cylinders 310. At this time, the moving unit 340 is moved along with the pistons 320. Simultaneously, the main shaft 400, which is coupled to the moving unit 340 through the link 350, is also moved upwards or downwards. Thereby, the sealing member 100 opens or closes the wafer moving passage.
Furthermore, as shown in FIG. 2, the valve drive unit 300 of the slit valve conducts a first driving step of moving the main shaft 400 upwards or downwards and a second driving step of moving the main shaft 400 forwards or backwards to open or close the wafer moving passage using the sealing member 100, that is, conducts an L-shaped driving action. To realize the L-shaped driving action, a guide slot having an shape is formed in the valve drive unit 300.
However, because the links 350 structurally form curved moving paths, in the case of the guide slot having a right-angled L shape, that is, having linear moving tracks, there is a problem in that it is difficult to precisely and smoothly guide the L-shaped driving movement of the valve drive unit 300.
Furthermore, as shown in FIG. 2, in the case where the link 350 is guided by the guide slot 351 having the right-angled L shape, stress concentration is induced at the corners of the link and the guide slot by repeated friction. In addition, when the link, which is inserted into the guide slot, is rotated around the corner of the guide slot, a small clearance undesirably occurs, as shown in FIG. 2. Thus, there is a problem in that the movement of the sealing member for opening or closing the wafer moving passage may not be precisely controlled.